There are two things to keep in mind: the natural growth habit of the plant you purchased and you are fertilizing and watering them.

As you know, there are different series of Ride The Wave Petunias that have different growth habits. Double check the tag to make sure you know which Wave series you are growing. You can get more info in the Which Wave is which? Section of this site.

Also, it could be how much you are feeding the plants. Again, Wave Petunias are heavy feeders and like lots of fertilizer to growth lush and strong. When planted in the ground, the plants get feed from the soil, so you only have to fertilize every two weeks or so. Obviously, containers and hanging baskets require more feeding – sometimes twice a week during the Summer.